Frequent Questions

Does the exclusion for laboratory wastewaters (Section 261.3(a)(2)(iv)(E) ) that contain small amounts of wastes that are listed as toxic wastes (T) also include wastes that are listed as toxic wastes (T) and as characteristic wastes, such as ignitability

The Section 261.3(a)(2)(iv)(E) exclusion from the mixture rule applies to wastes listed as toxic wastes and as characteristic wastes (i.e., I, C, or R). To meet this exclusion, the annualized average flow of laboratory wastewater into the facility headworks must not exceed one percent of the total wastewater flow or the estimated combined average concentration of toxic constituents entering the headworks or pretreatment facility must not exceed one part per million (ppm) (Section 261.3(a)(2)(iv)(E)). This requirement ensures that only small levels of toxic constituents are discharged and that the hazardous characteristic is removed by the waste mixing with the facility's nonhazardous wastewater stream. Facilities may use this mixture rule exclusion for wastes listed as toxic wastes and as characteristic wastes (i.e., I, C, or R), as long as their flow of laboratory wastewater does not exceed one percent of the total flow into the facility's headworks or the flow of toxic constituents does not exceed one ppm into the facility's headworks or pretreatment system. Although the wastewaters fall out of Subtitle C regulation through this exclusion, any sludges that are generated during wastewater treatment are subject to Subtitle C regulation if they exhibit a characteristic of hazardous waste.

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